A basic element for stylish living calls for optimum coordination between harmony and privacy in respect to the exposure to sunshine and conversely, protection from unwanted exposure to sunshine, to unwanted observation from a position outdoors, where the design of a living room or office is concerned. That is why it has become fashionable to employ the "double-layer" mode of design for Venetian blinds or window drapery for installation in a tasteful piece of housing. By the term "double-layer", reference is made to a regular Venetian blind, be it vertical or horizontal for execution, supplemented by a whole piece of window drapery side-by-side. The drapery is fitted further indoors, so that if and when it is intend to shade out sunshine completely, the blind is put down entirely, with the slats adjusted straight in the upstanding position, and the sunshine is kept out. But if it is then intended further to dim out light penetration, the drapery within can be pulled down to absorb and therefore keep out in full the light penetration, however small it might be, whereas illumination indoors can be adjusted solely with respect to the illumination facilities indoors. This arrangement not only eliminates the permeation of sunshine still prevailing where Venetian blind or window drapery alone is provided indoors, but also helps to block external noises, plus the additional advantage of tranquility and embellishing effects realized by virtue of pattern decor to be employed on the surface of the drapery.
In common practice, the preparation of so-called double-layer window drapery calls for separate installation, the drapery and the Venetian blind being structurally independent of each other, so that it is not infrequent to see fittings, locking bolts or brackets conflicting with each other as the installation is in progress, and even upon completion of the installation. The worst comes when it becomes extremely difficult to go ahead with the installation, or installation managed with inevitable deformations. Furthermore, the top rail and control being designed independent of each other, means not only a waste of structural economy, but also gross waste of labor involved in the installation. Moreover, it is rather complicated for use. All these explain why conventional composite blind-drapery window settings are far from being extensively accepted by the mass of consumers, in spite of its shading performance that is desirable.